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20 April 2014

Bob's Blog 20 April 2014

WEATHERGRAM
YOTREPS
Issued 20 April 2014: Easter Sunday
Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world of weather maps, so please fine-tune to your place.
Dates are in UTC unless otherwise stated.

SOI. The Southern Oscillation Index SOI sums up the weather pattern over the
South Pacific as one number. It is based on the standardized difference in
the barometer readings between Tahiti and Darwin.
SOI (30 day running mean) has been in the pink (below minus 10 in the
farmonlineweather.com graph for three weeks and relaxed a lot in the past
two weeks.

TROPICAL TOPICS
Tropical Cyclone ITA weakened quickly to Cat 1 over Queensland and then
re-deepened from 1000 to 980 hPa as it moved south along west coast of NZ on
Thursday to Saturdayas expected and mentioned in last weeks Weathergram.
The wind and rain damage for the start in Easter in NZ has been substantial.
In the Indian Ocean a tropical Low is possibly intensifying and is expected
to head SE perhaps towards the MH370 missing aircraft search area later this
week, but is expected to fade away before it gets there.

WEATHER ZONES
Panama to Galapagos: The wind flow over Panama and Las Perlas is expected to
be light and variable over the next few days. Also the wind flow for much of
the distance between Panama and Galapagos is expected to be form the SW this
week, no good for this voyage. And so it may be worthwhile waiting another
week (or more) for this trip, sad to say.

SPCZ South Pacific Convergence Zone
This is rather disjointed this week and rebuilding along the northern end of
its range from Solomons to Samoa.
A tropical LOW may form over Solomons by Wednesday and travel slowly SW into
the Coral Sea by the weekend, perhaps this may allow a trough to form over
Vanuatu and New Caledonia next week.

STR Sub-tropical Ridge
The STR has now shifted to its normal winter position, stretching from the
deserts of inland Australia across the North Tasman Sea and generally along
35 to 25S to the east of NZ. I'm not sure how long this pattern will last,
but it is the normal winter pattern, and if an El Nino episode kicks in then
it is the preferred pattern for the next few months.

New Zealand area
Trough is moving off to the east of NZ on Easter Monday.
HIGH in the north Tasman Sea is expected to move across the north of the
North Island on Wednesday/Thursday. A trough should cross the North Island
on Friday (ANZAC DAY)/Saturday, followed by another High travelling along
40S on Saturday/Sunday.
This is a good weather pattern for travel between NZ and the tropics to the
north, or vice versa. Enjoy!
However anyone attempting to sail across the Tasman Sea will need to be
watchful of large areas of light and variable wind. The SOLO TRANS TASMAN
YACHT RACE is departing from New Plymouth for Mooloolaba on Tuesday, so we
wish them well.

From Easter, the Double Ditch campaign has started with a kiwi attempting to
take a kayak from Coffs Harbour in Australia to New Plymouth in the NZ.
MetBob is helping with this adventure and you can follow its progress at
http://doubleditch.co.nz/tracking